The frame of an automotive vehicle supports an operator's compartment and includes a roof supported by generally vertical members commonly referred to as pillars. For vehicles referred to as pick-up trucks, the roof is normally supported by front and rear pillars, also known as the “A” and “B” pillars. The frame of the vehicle is required to withstand certain forces relating to crashes of the vehicle. Those crash standards help determine the configuration of the vehicle frame. Pick-up trucks are often designed with an enlarged operator's compartment that includes a rear passenger seat and a set of rear doors that can be hinged on the rear pillars to provide an open span between the front and rear pillars when the front and rear doors are opened.
This open span increases the longitudinal length of the roof and, as a result, increases the unsupported span over which load must be transferred to meet roof strength requirements and consequentially increases the moment applied to the base of the rear pillar of the operator's cab in a pick-up truck. The rear pillar is a critical contributor to the overall roof crush performance that allows up to five inches of deflection in which the load requirement must be met. The rear pillar becomes critical at the end of a crush test event as the rear pillar must contribute to the overall load absorbed by the operator's cab as the “A” pillar is first contacted and can only resist a given amount of the load. The rear pillar can be used to supplement the load resistance by the stiffness of the rear pillar.
Reinforcing the rear pillar in a pick-up truck is a design problem because the rear pillar conventionally has a large cross-sectional configuration and the packaging restraints include the rear door hinges, the rear door window, the back window and the seat belt restraints. Adding a large flat reinforcement to the rear pillar section is not likely to provide adequate benefits, as the reinforcement will tend to buckle under the imposed load instead of efficiently transferring the load.
In U.S. Pat. No. 5,123,696, issued to Tadayoshi Watari on Jun. 23, 1992, the rear pillar is provided with a reinforcement that forms a closed cross-section with the rear pillar inner panel. A pick-up truck having a rear door hinged to the rear pillar of the operator's cab is disclosed in U.S. Pat. No. 6,053,561, granted to Walter Hojnowski, et al on Apr. 25, 2000, wherein reinforcement plates are provided to reinforce the rear pillar. Similarly, the rear pillar is reinforced to improve crash performance in U.S. Pat. No. 6,705,668, issued to Masashi Makita on Mar. 16, 2004. In U.S. Pat. No. 6,827,390, granted to Robert Zummallen, et al on Dec. 7, 2004, the rear pillar is formed with inner and outer reinforcements that are welded to one another to form a box-like cross-section.
Accordingly, it would be desirable to provide a rear pillar design for a pick-up truck that would enhance roof strength while maintaining packaging constraints without utilizing large flat reinforcement members as is well known in the art.